Crossing the Mississippi at St Louis, we settle for the long haul across central Illinois and Indiana to Cincinnati. The Big Sky is at our backs as we leave the west firmly behind. The speed of life seems to quicken, accents change, and buildings pile up in what soon begins to look like one never-ending strip.

Today, it feels like we are entering the densely populated, industrialised east. Cincinnati was once among the boom towns that sprang up in what was then a remote wilderness at the western edge of the US, settled in part by former soldiers who were given land in return for their service in the revolutionary war. Later, it became a centre of trade by steamboat and railroad, and stood as a border city between the south and the north, slave states and free states.

It occupies a special place in American history as a major way-station along the Underground Railroad, a refuge for African Americans who crossed the Ohio river from Kentucky on their way to freedom. Quakers and other abolitionists provided safe houses where they could prepare for the journey north, and some found sanctuary in the basements and back rooms of Cincinnati's churches.

Allen Temple, a town that dates from 1808, was burned three times in the early nineteenth century by white gangs because its members helped hide fugitive slaves. At the Zion baptist church, a deacon put on a mock funeral in order to lead escaping slaves out of town.

The city's black churches still resonate with memories of two centuries of struggle, through Reconstruction and the civil rights movement. The struggles are by no means over. The city had a major race riot in 2001, when an unarmed black man was shot by Cincinnati police. For the African American community here, it was the breaking point after years of police misconduct and racial profiling.

With our crew in tow, Marc Maron visited the Rockdale baptist church for a special afternoon "homecoming" service, where the church welcomed back members and clergy who had moved on. We were greeted with great cordiality, fed, and given the full run of the place. Members proudly escorted Maron into the sanctuary, where the congregation was jubilant, dancing and singing along with the choir. Cries of "I am ready" rang out across the church.

"I am from the deep south," one man told us, choosing his words carefully as he spoke of the segregation that still persists in Cincinnati. "I experienced this all my life. It's time for a lift." Another said: "This country is going to rise up". They were talking about the Lord, but Barack Obama was at the front of their minds.

And for them, it is all intertwined: Obama's victory, if it comes, will come by the grace of God, a culmination of centuries of faith and struggle. It is hard for some of them to believe it could really happen. Yet his victory - and theirs - is starting to feel so close that they can almost reach out and touch it.